1. Field of the Invention
The present invention relates to a three-upright type transfer press, and more particularly to a method for separating and connecting a transfer bar capable of being separated into five bar pieces for use in the three-upright type transfer press and a device for practicing the method.
2. Description of the Prior Art
In conventional three-upright type presses having first and second movable bolsters, each of a pair of transfer bars is separated into five bar pieces, that is, an inlet side bar piece, first and second central bar pieces positioned above the bolsters, an intermediate bar piece positioned between the centeral bar pieces and an outlet side bar piece. The central bar pieces are capable of being taken in and out of the press body together with the movable bolsters, while the remaining bar pieces are let stand by between uprights.
The conventional separating sequence at the time of die change and connecting sequence after die change for the transfer bar constructed as above are as follows. Upon starting of die change, the transfer bar is moved to the outlet side of a workpiece. Then, the second movable bolster located on the outlet side is raised to support the second central bar piece positioned thereabove. In this state, the intermediate bar piece and the outlet side bar piece respectively connected to the left and right ends of the second central bar piece are separated from the second central bar piece. Thereafter, the first movable bolster is raised to support the first central bar piece positioned thereabove, and in this state the inlet side bar piece and the intermediate bar piece respectively connected to the left and right ends of the first central bar piece are separated from the first central bar piece. Thus, all the five bar pieces which constitute the transfer bar are separated from one another. In this separated state, the first and second movable bolsters respectively carrying thereon the first and second central bar pieces are drawn out from the press body and die change is performed. After the loading of a new die onto each movable bolster is completed, the movable bolsters are again pushed into the press body, and then the operation for connecting the five bar pieces is performed in accordance with the sequence reverse to that of the separating operation described above.
In the above-described conventional method, the two movable bolsters are raised successively, and the separating or connecting sequence is repeated at every rise of each movable bolster, thus requiring much time for the separation and connection of the transfer bar and thus resulting in deterioration of the working efficiency. For example, even when changing only the die on the first movable bolster, all of the foregoing separating and connecting sequences must be followed.